a. Field of the Invention
The instant invention relates to localization systems, such as those used in cardiac diagnostic and therapeutic procedures. In particular, the instant invention relates to a system and method for registering the coordinate frames of multiple such systems (e.g., a magnetic-based system and an impedance-based system) to common coordinate frames.
b. Background Art
The three-dimensional coordinates of a catheter or other medical device moving within a patient's body are often tracked using a localization system (sometimes also referred to as a “mapping system,” “navigation system,” or “positional feedback system”). These devices typically use magnetic, electrical, ultrasound, and other radiation sources to determine the coordinates of these devices. For example, impedance-based localization systems determine the coordinates of the medical device by interpreting a voltage measured by the medical device as a location within an electrical field.
Each different type of localization systems offers certain advantages and disadvantages. For example, an impedance-based localization system offers the ability to track numerous localization elements simultaneously, but is susceptible to inhomogeneities in the electrical field and “drift” resulting from varying impedance regions and other external factors. As used herein, the term “drift” refers to a stationary localization element appearing to move due, for example, to patient movement, respiration, electrical noise, varying impedance, and other external factors. Certain solutions to the disadvantages associated with inhomogeneous electrical fields and drift are described in U.S. application Ser. Nos. 11/227,580, filed 15 Sep. 2005; Ser. No. 11/715,919, filed 9 Mar. 2007; and Ser. No. 12/986,409, filed 7 Jan. 2011, all of which are incorporated by reference as though fully set forth herein.
Likewise, a magnetic-based system offers the advantages of improved homogeneity and less drift than an impedance-based system. Such systems, however, require special sensors to be used as localization elements and, as such, are relatively limited in the number of localization elements that can be simultaneously tracked.